The present invention relates to planar diaphragm type loudspeaker systems. More particularly, the invention relates to a driver unit for use in a planar diaphragm type loudspeaker system.
It is known that a planar diaphragm has acoustic pressure characteristics relatively flat over a wide frequency range without shifting of the acoustic image thus providing high fidelity sound reproduction. A variety of such type loudspeaker systems have been proposed. In conventional planar diaphragm type loudspeaker systems, loudspeaker units adapted to reproduce bass, mid and treble-ranges have been independently and separately mounted on a baffle board of the loudspeaker system. The planar diaphragms, although they were square in shape, were driven by circular driver units. This arrangement is, however, disadvantageous in that it is difficult for the circular driver unit to make the whole square planar diaphragm reciprocate uniformly. Furthermore, a voice coil for use in a planar diaphragm type loudspeaker unit is generally positioned in the vicinity of the planar diaphragm and air is sealed around the voice coil by the planar diaphragm and a magnetic circuit. Therefore, heat generated by the voice coil is cut off from escape resulting in a deterioration in the reproduction characteristics.
In such a multi-way planar diaphragm type loudspeaker system, in order to obtain improved acoustic pressure characteristics which are flat over a wide frequency range without shifting of the acoustic image, a coaxial multi-way planar diaphragm type loudspeaker system of simple construction has been proposed in co-pending U.S. Patent Application Ser. No. 164,128 filed on even date herewith by the instant applicant the specification of which is herein incorporated by reference. In this speaker system, square planar diaphragms for bass, mid, treble and, if desired, other ranges are coaxially arranged.